The present invention pertains generally to apparatus for forming annular slits or grooves in rod-shaped articles such as cigarette filter plugs, and pertains more specifically to such apparatus of a type adjustable to control the depth of the slit or groove and to accommodate rod-shaped articles of different diameters.
Annular grooves are conventionally provided in filter plugs and similar objects for various purposes. For example, annular grooves in a smoke-impermeable filter plug for admitting air into the filter interior to dilute the smoke stream are known. Certain gas-phase components of cigarette smoke are also known to be adsorbable on properly treated walls of annular or other grooves formed in the outer surface of a filter plug. A smoke-impermeable, generally annular groove provided in the filter plug can also be used to produced a venturi flow of the smoke stream toward the smoker's mouth.
Various methods for producing filter plugs with such grooves are known. Commonly, the groove is cut in a filter plug by means of a rotating knife of one kind or another, frequently a rotating disc knife. The knife can be heated if it is desired to heat-seal the groove surface. If the groove is to be relatively large and need not have rectilinear sides, grooves can be formed during extrusion of the filter plugs by means of periodic constriction of the extrusion die, as disclosed in U.S. Pat. No. 3,648,711, issued Mar. 14, 1972, to Berger et al.
Most frequently, when the groove is formed by cutting, the filter plug is held during the cutting operation in a groove or flute on the periphery of a rotating drum, to which the filter plug is held by means of vacuum suction. If a relatively rounded groove, rather than a sharply defined slit, is to be provided, a heated forming element can be used instead of a knife, as for example in U.S. Pat. No. 4,149,546, issued Apr. 17, 1979, to Luke et al.
Various other methods of rolling the filter plug between two elements one of which bears the formers or other device used to produce the desired groove or slit, are known. The former may be mounted on a generally annular or cylindrical guide adjacent to the surface of a rotating drum bearing the filter plug, the latter being free to rotate while being held against the drum, as in the '546 patent cited above. In U.S. Pat. No. 4,351,792, issued Sept. 28, 1982, to Sexstone et al., and U.S. Pat. No. 4,324,540, also to Sexstone et al., the filter plugs are fed from a hopper to a peripherally fluted drum, which carries the filter plugs to the top of a vertical gap defined between an endless belt and a column of stationary formers. The belt is driven to roll the filter plugs downward along the gap over the formers, which impart the desired shape to them.
Other methods of producing such filter plugs are known, such as spin-molding, disclosed in U. K. patent application No. 2 078 089.
It would be desirable to have an apparatus for providing annular slits or grooves in rod-shaped articles, such that the apparatus could be adjusted to accommodate articles of different sizes and to make the speed of movement of the article through the machine controllable independent of the rate of rotation of the article, unlike the rolling-type devices described above.
It is therefore the principal object of the invention to provide a simple, reliable apparatus capable of forming an annular groove or slit in a rod-shaped article such as a cigarette filter plug.
Another object of the invention is to provide such an apparatus in which the feed rate of the machine can be controlled independently of the rolling speed of the articles therein.
Another object of the invention is to provide such an apparatus capable of accommodating rod-shaped articles of different diameters.
Still another object of the invention is to provide such an apparatus adapted for forming such a slit of substantially uniform depth.